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transfer::data::source(n) 0.2 tcllib "Data transfer facilities"
transfer::data::source - Data source
- package require Tcl 8.4
- package require snit ?1.0?
- package require transfer::copy ?0.2?
- package require transfer::data::source ?0.2?
This package provides objects mainly describing the origin of some data to transfer. They are also able to initiate transfers of the described information to a channel using the foundation package transfer::copy.
- transfer::data::source objectName ?options...?
This command creates a new data source object with an associated Tcl command whose name is objectName. This object command is explained in full detail in the sections Object command and Object methods. The set of supported options is explained in section Options.
The object command will be created under the current namespace if the objectName is not fully qualified, and in the specified namespace otherwise. The fully qualified name of the object command is returned as the result of the command.
All objects created by the ::transfer::data::source command have the following general form:
- objectName destroy
This method destroys the object. Doing so while a transfer initiated by the object is active is safe as all data required for the transfer itself was copied, and the completion of the transfer will not try to access the initiating object anymore. i.e. the transfer is completely separate from the source object itself.
- objectName type
This method returns a string describing the type of the data the object is refering to. The possible values and their meanings are:
No data was specified at all, or it was specified incompletely. The object does not know the type.
The data to transfer is contained in a string.
The data to transfer is contained in a channel.
- objectName data
This method returns a value depending on the type of the data the object refers to, through which the data can be accessed. The method throws an error if the type is undefined. For type string the returned result is the data itself, whereas for type channel the returned result is the handle of the channel containing the data.
- objectName size
This method returns a value depending on the type of the data the object refers to, the size of the data. The method throws an error if the type is undefined. Return of a negative value signals that the object is unable to determine an absolute size upfront (like for data in a channel).
- objectName valid msgvar
This method checks the configuration of the object for validity. It returns a boolean flag as result, whose value is True if the object is valid, and False otherwise. In the latter case the variable whose name is stored in msgvar is set to an error message describing the problem found with the configuration. Otherwise this variable is not touched.
- objectName transmit channel blocksize done
This method initiates a transfer of the referenced data to the specified channel. When the transfer completes the command prefix done is invoked, per the rules for the option -command of command transfer::copy::do in the package transfer::copy. The blocksize specifies the size of the chunks to transfer in one go. See the option -blocksize of command transfer::copy::do in the package transfer::copy.
All data sources support the options listed below. It should be noted that the first four options are semi-exclusive, each specifying a different type of data source and associated content. If these options are specified more than once then the last option specified is used to actually configure the object.
This document, and the package it describes, will undoubtedly contain bugs and other problems. Please report such in the category transfer of the Tcllib Trackers. Please also report any ideas for enhancements you may have for either package and/or documentation.
Copyright © 2006-2009 Andreas Kupries <firstname.lastname@example.org>